Attachment plug base



March 22, 19.49. L LUDWIG 2,464,876

ATTACHMENT PLUG BASE Filed June 11, 1946 INVENTOR au/5 u ovv/G BY fTORNEY Patented Mar. 22, 1949 UNITED STATES PATENT OFFICE ATTACHMENTPLUG BASE Louis Ludwig, Brooklyn, N. Y.

Application June 11, 1946, Serial No. 675,872

3 Claims. l

This invention relates to attachment plug bases and, more particularly,to attachment plug bases whose bodies include two similar molded halves.

Heretofore these molded halves had threads integrally formed on theirexternal surfaces, and therefore required separate mold cavities toprovide matching thread ridges. Furthermore, because of the threads, atubular terminal shell which held the two halves together had to bethreaded onto the body.

It is the main object of my invention to provide an attachment plug baseof the character described whose two body halves are identical, ratherthan merely similar, whereby to reduce mold expense, and which halvesare so constructed that the terminal shell can be pushed on, rather thanthreaded into place, whereby to reduce assembly expense.

It is another object of my invention to provide an attachment plug baseof the character described in which the contact ngers are xedly held inposition simply by permanently mounting the terminal shell and Withoutthe use of any other means.

It is a further object of my invention to provide an attachment plugbase of the character described in which the side contact finger isalways in good electrical Contact with the terminal shell and in whichthe contact pressure between said finger and shell will be increasedwhen a jack blade is inserted in the plug base.

Other objects of my invention will in part be obvious and in part behereinafter pointed out.

The invention accordingly consists in the features of construction,combinations of elements and arrangement of parts which will beexemplied in the construction hereinafter described and of which thescope of application will be indicated in the claims.

In the accompanying drawings, in whichl is shown one of the variouspossible embodiments of my invention,

Fig. 1 is a front view of an attachment plug base constructed inaccordance with my invention;

Fig. 2 is a top View thereof;

Figs. 3 and 4 are sectional views taken substan tially along the lines3-,3 and d-ll respectively of Fig. 2;

Figs. 5 and4 G are sectional views taken substantially alongthe lines5-5 and 6-6 of Fig. 3; and

Fig. 'I is a bottom view of the plug base.

In, general, I accomplish the objects of my invention by providing ahollow casing of electrical insulating material which is split into twohalves along a plane including the axis of symmetry of the casing andpassing through plug-blade-admitting slots inthe top wall of the casing.The two halves are provided with mating recesses and indentations ofdifferent sizes and shapes which cooperate to firmly and captively mountwithin the casing at least one pairof spaced contact lingers when thetwo halves of the casing are secured together. The contact fingers havesuitable extensions running to the outside of the casing, one beneaththe casing at the center thereof and the other at the side of thecasing. The central extension serves as one of the contact terminals ofthe plug base. The side extension engages an'electrically conductiveterminal shell which surrounds the side walls of the casing. This shell,which forms the other contact of the plug base, is threaded to enable itto be screwed into an electrical socket. Although the shell is threaded,the casing is not, so that the shell can easily slip into position. Tohold the shell against axial displacement once it is in position, thecasing is provided with an annuuar channel into which the top edge ofthe shell is spun. In addition, the casing may have one or morenon-annular depressions to receive tines or projections struck from theshell whereby to prevent relative angular movement of the shell andcasing.

Referring now to the drawings, it denotes an attachment plug baseconstructed in accordance with my invention and adapted to be used inconjunction with a conventional male jack, the blades of which aredetachably receivable in the plug base. Said plug base comprises acasing I2 of electrical insulating material, such, for example, as hardrubber or a phenolic condensation resin in which are contained twoelectrically conductive I contact fingers I4, i6. A shell I8, ofelectrically conductive material, holds the various parts of the plugbase together.

The casing l2 includes two identical halves 2t, 2t (see Fig. 2) whichwhen assembled are disposed in registry and abutment along a plane 23,including the axis of symmetry of the casing. Due to the identity inconstruction of the two halves only the half 2l) will be described, and,for convenience, the same elements of the other half 22 will beidentified by the same reference numerals primed.

The half 20 is approximately semi-cylindrical, the saine comprising anarcuate side wall 24 which is semi-circular in cross-section (see Figs.5 and 6). The upper end 2d of said half is .fiared out like aAgonventional plug base to facilitate turning. Said upper end carriesaintegral top wall 28 forming one half of the top surface of the plugbase. This wall has a pair of indentations 30 which cooperate withmating indentations 30 in the other half 22 to provide spaced slots 3|for the reception of plug blades. Said top wall may be plain or, ifdesired, the same may be ornamented as indicated in the drawings.

The lower end of the half 20 includes an integral bottom wall 32 whichcooperates with the mating bottom wall 32 of the half 22 to close theunderside of the plug base. The wall 32 is of lesser diameter tha-n theside wall 24 in order to form an inset shoulder 34 between the bottomside walls of the plug base, the purpose of which will shortly be madeclear.

The external surface of the arcuate side Wall is smooth anduninterrupted save for two depressions now to be described and a slotwhich will be described later. The iirst of these depressions is asemi-annular groove 35, which, in conjunction with the matingsemi-annular groove 36' forms a continuous circumferential groove aroundthe casing |2. The second depression constitutes a non-annularindentation 38 which may, as shown, be :contiguous with the groove 36.The groove 36 is located beneath the upper edge of the shell I8 and thedepression 38 is disposed at any place within the region of the arcuateside wall covered by said shell.

The shell i6 is of tubular shape, having a thread 39 integrally formedtherein. The lower edge of the shell terminates in an inturned flange 46which is abutted against the shoulder 34 during assembly of the plugbase. The upper edge 42 of said shell overlies the groove 36 and is spuninto said groove as one of the nal steps in the assembly of the plugbase, a tine 44 being struck from said shell to enter the depression 33either at the same time that the edge 42 is spun in or immediatelybefore or after the spinning operation.

To reinforce the weak spots in the casing the half 20 has a ridge 46raised on the interior surface thereof in back of the groove 36 and aflat 48 built up in back of the depression 38.

The interior of the casing is hollow to accommodate the elongatedcontact fingers I4, I6, the same being fabricated from any resilientmaterial well-known to the art. At least two :contact :lingers areemployed, to wit, the center contact f linger |4, so-called because itis in electrical contact with the bottom central terminal, and the sidecontact finger, so-called because it is in electrical contact with theshell 8. vBoth contact lingers may be formed from a ribbon of sheetmetal by any suitable bending and shaping operations.

The center contact finger 4 includes a shank 50 disposed beneath one ofthe slots 3| and adapted to be frictionally engaged by a plug blade. Atits upper end said shank has an Outwardly inclined tip 52 which lies ona shelf 54 formed on the inner surface of the half 26 and located belowand radially outwardly of the slot 3|. Said shelf is shallower than thewidth of the ribbon from which the contact finger I4 is formed, thedepth of the shelf being such that when the tip 52 is placed on theshelf during assembly of the plug base, approximately one half of saidtip will be received in the pocket formed by the shelf and the otherhalf of the finger will extend above said pocket. In this fashion themating shelves 54, 54' in the two halves of the casing cooperate toprovide a recess which snugly receives the tip 52 and prevents thecontact finger I4 from shifting transversely of itself. The bottom wall56 of the shelf 54 is sloped, as indicated, to approximately match theslope of the tip 52, thus forming a substantial area of support for saidtip.

The lower end of the finger I4 is formed into a proper shape to providea bottom central terminal for the plug base. For this purpose the shank50 has a dependent inwardly inclined integral leg 58 carrying a U-shapedextension 60, the base 62 of which rests against the bottom wall of thecasing. Said base may, if desired, be provided with a raised boss 64 toexpedite electric contact. The two sides of the U-shaped extension 54are snugly received in slots 66 in the bottom wall 32 of the half 2|).These slots, like the shelf 54, have a depth of approximately equal toone-half the width of the linger I4, so that the opposed slots 66, 66 inthe two halves of the casing cooperate to define openings in the bottomwall of the plug base through which the U-shaped extension first passesfrom the inside to the outside of the plug base and then from theoutside to the inside of said base. This construction makes certain thatthe finger is securely locked in position. The linger is prevented fromsliding axially, when the plug base is half assembled, by an outwardlyinclined tip 68 projecting from the free end of the U-shaped extension.If desired, the bottom wall 32 may be provided with a depressed portion'l0 intermediate the slots 66 to secure an opening beneath the boss 64and thus lend some degree of resilience thereto.

The side contact nger IB includes a shank 12 located beneath the otherslot 3| and having an upper outwardly inclined extension 14 receivedupon a shelf 'I6 on the inner surface of the half 20. Depending from thelower end of the shank 62 is a right-angled outwardly extending leg 18which passes through a slot in one edge of said half. This legterminates in an upwardly extending tip 82 which lies against theoutside of the side wall of the half. Said slot 80 has a depth equal toapproximately one half of the width of the linger I6 so that the matingslots 80, 86 on the two halves will cooperate to lock the finger inplace at this point. The tip 82 preferably lies immediately belowthegroove 36vso that the shell i8 can be forced against the ,same whenits upper edge 42 is spun in.

It will be appreciated that with this construction when a plug bladeengages the shank 'l2 of the side finger contact I6 it will force thetip B2 outwardly increasing the pressure with which it4 engages theshell I8.

It will thus be seen that I have provided an attachment plug base whichachieves the several objects of my invention and which is well adaptedto meet the conditions of practical use.

As various possible embodiments might be made of the above invention andas various changes might be made in the embodiment above set forth, itis to be understood that all matter herein described or shown in theaccompanying drawings is to be interpreted as illustrative and not in alimiting sense.

Having thus described my invention, I claim as new and desire to secureby Letters Patent:

1. An attachment plug base comprising a cylindrical casing of insulatingmaterial, said casing including two identical halves abutted along aplane including the axis of symmetry of said casing, the side walls ofsaid casing being free of threads, a pair of contact fingers containedwithin said casing, each half of the casing having a top wall with apair of spaced slots adapted to cooperate with mating slots in the otherhalf to form openings for passing a pair of plug blades, means withinsaid casing to captivelyand rmly secure said contact iingers beneathsaid openings whereby the same may be frictionally engaged by the plugblades, each said half having a bottom wall inset from the side walls toform a shoulder, a terminal shell having a screw thread integrallyformed thereon, means integrally extending from the bottom edge of saidshell and abutted against said shoulder, a depression in one of saidhalves, means extending 'inwardly from said shell and received withinsaid depression to prevent rotation of said shell, one of said contactngers having an integral extension projecting through the bottom wall ofthe casing to form a central contact for the plug base and the other ofsaid ngers having an integral extension projecting through a side wallof the casing and in contact with said shell, said shell beingimperforate in the region of said other finger, and an annular grooveextending around said housing near the upper edge o-f said shell, saidgroove receiving an inwardly spun flange on said upper edge of the shellsaid other finger being near said inwardly spun flange, whereby saidother finger is caught between the shell and the outer surface of thecasing and thus is in intimate Contact with the shell.

2. An attachment plug base comprising a cy lindrical casing ofinsulating material, said casing including two identical halves abuttedalong a plane including the axis of symmetry of said l casing, the Sidewalls of said Casing being free of threads, a pair of contact fingerscontained within said casing, each half of the casing having a top wallwith a pair of spaced slots adapted to cooperate with mating slots inthe other half to form openings for passing a pair of plug blades, meanswithin said casing to captively and rmly secure said contact fingersbeneath said openings whereby the same may be frictionally engaged bythe plug blades, each said half having a bottom wall inset from the sidewalls to form a shoulder, a terminal shell having a screw threadintegrally formed thereon, means integrally extending from the bottomedge of said shell and abutted against said shoulder, a depression ineach of said halves, means extending inwardly from said shell andreceived within said depressions whereby to captively secure said shellto said casing, and an annular groove extending around said housing nearthe upper edge of said shell, said groove receiving an inwardlyextending flange on said upper edge of the shell, the sides of saidcasing halves having mating slots which cooperate to form openings, oneof said contact fingers having an outwardly extending portion passingthrough said openings and a finger on the end of said outwardlyextending portion Which is disposed beneath the shell in the region ofthe inwardly spun upper flange whereby said finger is caught between theshell and the outer surface of the casing.

3. An attachment plug base comprising a cylindrical casing of insulatingmaterial, said cas- 'ing including two identical halves abutted along aplane including the axis of symmetry of said casing, the side walls ofsaid casing being free of threads, a pair of contact fingers containedwithin said casing, each half of the casing having a top wall with apair of spaced slots adapted to cooperate with mating slots in the otherhalf to form openings for passing a pair of plug blades, means withinsaid casing to captively and rmly secure said contact ngers beneath saidopenings whereby the same may be frictionally engaged by the plugblades, each said half having a bottom wall inset from the side walls toform a shoulder, a terminal shell having a screw thread integrallyformed thereon, means integrally extending from the bottom edge of saidshell and abutted against said shoulder, and an annular groove extendingaround said housing near the upper edge of said shell, said groovereceiving an inwardly spun flange on said upper edge of the shell, the`sides of said casing halves having mating slots which cooperate to formopenings, one of said iingers having an outwardly extending portionpassing through said openings and a nger on the end of said outwardlyextending portion which is disposed beneath the shell in the region ofthe inwardly spun upper ange, said shell being imperforate in the regionof said iinger whereby said iinger is caught between the shell and theouter surface of the casing and is in intimate contact with the shell.

LOUIS LUDWIG.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,373,127 Freeman Mar. 29, 19211,875,270 Slade et al Aug. 30, 1932 2,210,603 Shaw Aug. 6, 1940

